Flowers, pollination, seeds

A flower is a sex organ. That's the whole thing. Every striking trait (color, shape, scent) evolved to solve one problem: moving pollen from one plant to another, usually with an animal's help.

Four sets of parts

• Sepals: usually green, protect the bud.
• Petals: the advertisement. Some patterns recur worldwide, and botanists call them pollination syndromes: red, tubular, scentless flowers tend to draw hummingbirds; yellow and blue flowers with ultraviolet markings invisible to us tend to draw bees; pale, heavily scented flowers opening at dusk tend to draw moths. Treat these as tendencies rather than rules. When botanists have gone out and recorded who actually visits, the classic syndromes correctly predict the main pollinator for only about a third of species (Fenster et al., 2004; Ollerton et al., 2009).
• Stamens (male): a filament topped by an anther that makes pollen.
• Pistil (female): a sticky stigma, a style, and an ovary holding the ovules.

Petal Sepal Stamen Stigma Style Ovary

Fig. 11. Sepals and petals frame the reproductive parts. Stamens (male) make pollen; the pistil (female) is the stigma, style, and ovary, which holds the ovules that become seeds.

Pollination to seed

Pollination moves pollen from anther to stigma. The grain grows a tube down the style to an ovule, a sperm cell fuses with the egg (fertilization), the ovule becomes a seed, and the ovary often swells into a fruit that carries the seed away from the parent.

Why it matters for care

Mostly you grow houseplants for foliage, so this is incidental. Indoor edibles are the exception, and they differ more than you'd expect. Tomatoes are the demanding case: their pollen sits locked inside the anthers and is released only by vibration at the right frequency, the trick bumblebees perform and honeybees cannot. Hold a running electric toothbrush against the flower cluster's stem, not the bloom itself, which bruises, for a second or two every other day (Pundt, 2017; Mississippi State University Extension Service, n.d.). Peppers are self-pollinating and will set fruit unassisted, but vibration or a soft brush gives bigger, better-filled fruit (Roldán Serrano & Guerra-Sanz, 2006). Strawberries will also set unassisted, but unpollinated parts of the fruit simply don't swell, which is why indoor berries come out lopsided; brush gently across the whole center of each open flower (Klatt et al., 2014). And fruiting is metabolically expensive, pulling sugar away from leaf and root growth.